Covering AC Condensers in the Winter

I sometimes see AC condenser units covered in the winter months but most of the time I see then left exposed. It seems the main benefit of the covers is they keep debris and tree litter from getting inside the unit. Are there any negatives to these covers (ie - trapping and holding moisture inside the unit)?

Re: Covering AC Condensers in the Winter

A cover that protects the top of the unit, fan can be a good thing but The sides should not be covered so that you don't encourage rodents to make homes.
An old plastic trash can lid makes a good cover.

Re: Covering AC Condensers in the Winter

I have been told by a couple HVAC contractors that they love to see folks wrap and cover their units with plastic. Why? They both said that they know the fan will need to be replaced that summer or sooner than normal!

They both said that it is best to place a piece of plywood on top to cover the top of the unit. Weight it down with a brick or two but it is important to leave the sides open. This will keep stuff out of the unit and also keep snow and ice from sitting on/in the fan motor.

Re: Covering AC Condensers in the Winter

Originally Posted by Scott Patterson

I have been told by a couple HVAC contractors that they love to see folks wrap and cover their units with plastic. Why? They both said that they know the fan will need to be replaced that summer or sooner than normal!

They both said that it is best to place a piece of plywood on top to cover the top of the unit. Weight it down with a brick or two but it is important to leave the sides open. This will keep stuff out of the unit and also keep snow and ice from sitting on/in the fan motor.

Great advice, Scott. We're based in Chicago A/C market, so the winters are pretty tough here. Covering the top of the condenser will certainly keep a majority of the debris out of your unit, but as long as yearly maintenance is being performed in the unit, this shouldn't even be a concern since the debris will be removed anyway! We've even seen cages around the AC units, though we're pretty sure it's to prevent copper theft, not animal nesting.

Re: Covering AC Condensers in the Winter

Originally Posted by Rod Butler

YES cover the condensing unit for the same reason you cover your BBQ grille....

Rod, I guess you don't grill in the winter.
My grill is used all year around, and having to take a stiff and/or brittle cover off or trying to get the snow off without damaging the grill cover just doesn't hack it. I have not seen any issues within the grill, and a spray can of black fixes the looks on the outside.
The reason that I heard NOT to cover your condensing unit in the winter, is that a cover over the unit causes condensation to continuously build up in within the unit causing rust or oxidation on the respective metals, as well as premature paint failure.
From a HVAC person that loves people covering their units.

Re: Covering AC Condensers in the Winter

Originally Posted by Rich Goeken

Rod, I guess you don't grill in the winter.
My grill is used all year around, and having to take a stiff and/or brittle cover off or trying to get the snow off without damaging the grill cover just doesn't hack it. I have not seen any issues within the grill, and a spray can of black fixes the looks on the outside.
The reason that I heard NOT to cover your condensing unit in the winter, is that a cover over the unit causes condensation to continuously build up in within the unit causing rust or oxidation on the respective metals, as well as premature paint failure.
From a HVAC person that loves people covering their units.

I too grill all year long but I still cover my grill and I don't need to spray it to keep it looking new. But then I keep it covered year round.

But to address your main point, which is condensation: why would condensation occur when the outside temp is the same as the inside temp (of the condensing unit)?

And more to the point, if condensation were to occur would it be any less damaging than three feet of snow and ice? Consider water getting between the condenser fins and then going thru multiple freeze-thaw cycles, or ice building up inside of the cabinet.

Not trying to be confrontational Rich, I just don't understand the logic of not covering during the winter.

Re: Covering AC Condensers in the Winter

Seems to me that condensers are designed to be out in the weather year round. Manufacturer's are pretty specific about how their equipment is to be maintained and I don't recall ever seeing a spec requiring protection from the elements. Sounds more like some A/C cover manufacturer's marketing worked quite well.

Re: Covering AC Condensers in the Winter

Originally Posted by Eric Barker

Seems to me that condensers are designed to be out in the weather year round. Manufacturer's are pretty specific about how their equipment is to be maintained and I don't recall ever seeing a spec requiring protection from the elements. Sounds more like some A/C cover manufacturer's marketing worked quite well.

Re: Covering AC Condensers in the Winter

Being a HVAC/R contractor for many years, I love to see clients that cover thier condensors in the winter. I always explain that they should not be covered for the following reasons:
1. The cover causes the condensing unit to hold moisture causing the unit to rust out.
2. The cover causes the condener fan motor bearings to sieze requiring a new motor.
3. The cover encourages rodents to make a home within; they will normally add with wiring insulation to thier diet.
The list can go on and on.
I try to explain to the clients that the A/C condensing unit is outside in the rain all summer long with no problems, it is not going to be harmed by the snow. If they insist then want to cover it, I recommend only placing a piece of plywood the same size as the unit itself on the top. The will allow the air to circulate and not hold moisture inside nor will it invite the critters from the area to make a new home.

Re: Covering AC Condensers in the Winter

Originally Posted by Richard Johnson

Being a HVAC/R contractor for many years, I love to see clients that cover thier condensors in the winter. I always explain that they should not be covered for the following reasons:
1. The cover causes the condensing unit to hold moisture causing the unit to rust out.
2. The cover causes the condener fan motor bearings to sieze requiring a new motor.
3. The cover encourages rodents to make a home within; they will normally add with wiring insulation to thier diet.
The list can go on and on.
I try to explain to the clients that the A/C condensing unit is outside in the rain all summer long with no problems, it is not going to be harmed by the snow. If they insist then want to cover it, I recommend only placing a piece of plywood the same size as the unit itself on the top. The will allow the air to circulate and not hold moisture inside nor will it invite the critters from the area to make a new home.

Richard, your argument makes no sense. Your car or truck is made to be outside in the rain and snow as well but keeping in a garage when not driving seems to extend the life. Sure the manufacturer doesn't say it has to be garaged but they are in the business of selling cars. The sooner your old one wears out the sooner you buy a new one. See any correlation here?

And I still don't understand why condensation would occur and even if it did why that is worse than snow, ice and rain.

Re: Covering AC Condensers in the Winter

I checked Trane, Carrier, York, Rheem, Lennox, Goodman and Nordyne websites for User Manuals and FAQs regarding covering air conditioning units in the winter months. Rheem and Lennox were the only manufacturers who addressed the question directly. Others just mentioned keeping the outdoor unit free of dirt and debris and not draping or covering the unit during operation.

Frequently Asked Questions
Should outdoor units be covered in winter? No. Rheem heat pumps operate year-round and should never be covered. Similarly, air conditioners that operate seasonally are built to withstand an outdoor environment and should not be covered.

Should I cover my outdoor unit in the fall and winter?
Covering the unit is not necessary, especially if you have a heat pump that runs all year long. In fact, covering an entire unit may actually trap moisture. If you're concerned about leaves and debris getting inside the housing, short covers are available as an optional accessory and may be purchased through your local Lennox dealer.

Re: Covering AC Condensers in the Winter

Originally Posted by Rod Butler

Richard, your argument makes no sense. Your car or truck is made to be outside in the rain and snow as well but keeping in a garage when not driving seems to extend the life. Sure the manufacturer doesn't say it has to be garaged but they are in the business of selling cars. The sooner your old one wears out the sooner you buy a new one. See any correlation here?

And I still don't understand why condensation would occur and even if it did why that is worse than snow, ice and rain.

And the list can go on and on.

Your roof may actually last longer if you cover it too! Moister from snow and rain dry faster on an uncovered unit. The rodent problem is real whether you cover or not, they actually nest quite well around the contactor.

Re: Covering AC Condensers in the Winter

Originally Posted by Rod Butler

Richard, your argument makes no sense. Your car or truck is made to be outside in the rain and snow as well but keeping in a garage when not driving seems to extend the life. Sure the manufacturer doesn't say it has to be garaged but they are in the business of selling cars. The sooner your old one wears out the sooner you buy a new one. See any correlation here?

And I still don't understand why condensation would occur and even if it did why that is worse than snow, ice and rain.

And the list can go on and on.

1. Your automobile is used on a frequent (usually daily) basis during the winter whereas your A/C unit is not.
2. Putting your vehicle in a garage is not similar to the tightly enclosed space of an A/C cover. A more accurate analogy would be a car cover - which, from my understanding, are not recommended, either.
3. Enclosing an outdoor fixture increases radiant heat - which can cause the inner temperatures to raise above ambient temperature. This increase in temperature, even during winter, is enough to raise it above freezing, causing condensation. The restrictive airflow caused by the enclosure keeps this condensation from evaporating, and then it freezes at night at the absence of radiant heat. This cycling of solidifying and liquefying can also cause the unit's components to expand and contract making them more susceptible to breakage.

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